Applications in which an amplification gain of a variable amplifier is to be controlled are various. In digitizer circuits, variable amplifiers may be used to pre-amplify an analog signal for a subsequent analog-to-digital converter. When the analog signals to be digitized have a high dynamic range, which corresponds to an amplitude varying by a considerable amount, it may be necessary to adjust the amplification gain of the amplifier so as to not operate the analog-to-digital (A/D) converter outside of its dynamic range. That is saturation of the A/D converter should be avoided. Saturation of the A/D converter can be detected by an inspection of the digital signal provided by the A/D converter. When subsequent samples of the digital signal have the maximum digital value of the A/D circuit, one may assume that the A/D converter is operated with an analog signal having an amplitude beyond the capability or range of the A/D converter. Even though one may use more complicated criteria in the digital domain, such as for example predictive filters to detect that the A/D converter is about to be saturated, the detection may take too long in order to avoid saturation, in particular in the presence of signals with a high dynamic range and high slew-rates. Signals with high slew-rates have amplitude that varies strongly over short periods of time. Hence, it may not be feasible to adapt the amplification gain of an amplifier timely enough to avoid saturation of the A/D converter, which may result in a degradation of the signal quality in the digital domain, for example, when a signal of a microphone has to be digitized. This may, for example, even result in a listener which is no longer capable of understanding the voice of a speecher, e.g. during a podium discussion or within a telephone conference.
Hence, there appears to be a desire to improve the control of an amplification gain of an amplifier for amplifying a signal with a high dynamic range.